The 27-year-old athlete had sustained a severe laceration to her liver and a collapsed right lung in a crash during a final practice July 30.

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Arielle Martin was knocked out of the London Olympics last week when she crashed during practice. She also crashed during the quarterfinals of the world championships in 2008.

Updated at 6:39 AM CST on Monday, Aug 6, 2012

BMX rider Arielle Martin of the United States has had surgery after injuring her liver and lung in a crash during practice last week that knocked her out of the London Olympics.

Martin's family said in a statement Sunday that the medal contender had a setback after she was upgraded from intensive care to a trauma unit. The 27-year-old athlete had sustained a severe laceration to her liver and a collapsed right lung in a crash during a final practice July 30.

The operation removed a buildup of fluid, the statement said.

"She came through it like the champ she is and this should help the healing process," said her mother, Lori Martin. "She is aware of all the well-wishes."

USA Cycling did not announce the injury until Wednesday, when it said 19-year-old Brooke Crain would replace Martin on the Olympic roster. The team left for London the same day.

USA Cycling also did not reveal the nature or severity of the injuries.

Martin's family said the crash was caused by a "mechanical malfunction" during a training run in Chula Vista, Calif. Martin was taken to Scripps Mercy Hospital in San Diego, where her injuries were initially deemed life-threatening.

Martin would have been competing in her first Olympics.

She also crashed during the quarterfinals of the world championships in 2008, which allowed her friend Jill Kintner to finish high enough to overtake Martin for the automatic spot at the Beijing Games, when BMX made its Olympic debut. Kintner won the bronze medal.

Martin has said missing the Beijing Games made her more determined to compete in London.

"Arielle is one of the most talented and determined athletes I've ever had the pleasure to work with," said Mike King, who runs the BMX program for USA Cycling. "Her leadership and character will be missed both on and off the track."

The BMX competition begins Wednesday with seeding runs at the Olympic Park.

The U.S. qualified two women for the London Games. Crain will be joined in the competition by Alise Post, who made the team as a discretionary selection.

"Arielle has been such a good leader to all of us, and she has helped us all to where we are now," Crain said. "I've been put in a situation to help my team and I am now focused and eager to take to the track and represent my country well."

Despite her age, Crain has already established herself as one of the top BMX riders, and should be in contention for an Olympic medal. She was ranked No. 1 in the world earlier this year, and was third behind Martin and Post in the most recent USA Cycling power rankings.

Crain finished sixth at the world championships in May.

"Brooke has posted consistent international results," King said, "has been training hard and is fully prepared to step in and make an impact in London."